Useful R functions

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Sandbox vectors

Let’s define some vectors which can be used for demonstrations:

manyNumbers <- sample( 1:1000, 20 )
manyNumbers

 [1] 204 164 724 546 631 526 874  77 914 174 453 455 103 528 913 471 960  74 710 529

manyNumbersWithNA <- sample( c( NA, NA, NA, manyNumbers ) )
manyNumbersWithNA

 [1]  NA 710 914 874 204 164  NA 529 528 546 526 913 724  NA 631  77 453 174 471  74 455 103 960

duplicatedNumbers <- sample( 1:5, 10, replace = TRUE )
duplicatedNumbers

 [1] 2 3 4 5 3 3 2 4 1 5

letters

 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"

LETTERS

 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z"

mixedLetters <- c( sample( letters, 5 ), sample( LETTERS, 5 ) )
mixedLetters

 [1] "r" "e" "c" "l" "b" "N" "G" "J" "A" "H"

Are all/any elements TRUE

• Input: logical vector
• Output: single logical value
• Task: try, understand what happens when you use manyNumbersWithNA instead of manyNumbers.

all( manyNumbers <= 1000 )

[1] TRUE

all( manyNumbers <= 500 )

[1] FALSE

any( manyNumbers > 1000 )

[1] FALSE

any( manyNumbers > 500 )

[1] TRUE

all( !is.na( manyNumbers ) )

[1] TRUE

any( is.na( manyNumbers ) )

[1] FALSE

Which elements are TRUE

Input: logical vector Output: vector of numbers (positions)

which( manyNumbers > 900 )

[1]  9 15 17

which( manyNumbersWithNA > 900 )

[1]  3 12 23

which( is.na( manyNumbersWithNA ) )

[1]  1  7 14

Filtering vector elements

• Input: any vector and filtering condition
• Output: elements of the input vector
• Note: several ways to get the same effect

manyNumbers[ manyNumbers > 900 ] # indexing by logical vector

[1] 914 913 960

manyNumbers[ which( manyNumbers > 900 ) ] # indexing by positions

[1] 914 913 960

somePositions <- which( manyNumbers > 900 )
manyNumbers[ somePositions ]

[1] 914 913 960

Are some elements among other elements

• Input: two vectors
• Output: a logical vector corresponding to the first input vector

"A" %in% LETTERS

[1] TRUE

c( "X", "Y", "Z" ) %in% LETTERS

[1] TRUE TRUE TRUE

all( c( "X", "Y", "Z" ) %in% LETTERS )

[1] TRUE

all( mixedLetters %in% LETTERS )

[1] FALSE

any( mixedLetters %in% LETTERS )

[1] TRUE

mixedLetters[ mixedLetters %in% LETTERS ]

[1] "N" "G" "J" "A" "H"

mixedLetters[ !( mixedLetters %in% LETTERS ) ]

[1] "r" "e" "c" "l" "b"

manyNumbers %in% 300:600

 [1] FALSE FALSE FALSE  TRUE FALSE  TRUE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE  TRUE FALSE  TRUE FALSE
[18] FALSE FALSE  TRUE

which( manyNumbers %in% 300:600 )

[1]  4  6 11 12 14 16 20

sum( manyNumbers %in% 300:600 )

[1] 7

Pick one of two (three) depending on condition

• Input: a logical vector and two vectors additional vectors (for TRUE, for FALSE)
• Output: elements of the additional vectors
• Note: it can take care of NAs

if_else( manyNumbersWithNA >= 500, "large", "small" )

 [1] NA      "large" "large" "large" "small" "small" NA      "large" "large" "large" "large" "large" "large"
[14] NA      "large" "small" "small" "small" "small" "small" "small" "small" "large"

if_else( manyNumbersWithNA >= 500, "large", "small", "UNKNOWN" )

 [1] "UNKNOWN" "large"   "large"   "large"   "small"   "small"   "UNKNOWN" "large"   "large"   "large"  
[11] "large"   "large"   "large"   "UNKNOWN" "large"   "small"   "small"   "small"   "small"   "small"  
[21] "small"   "small"   "large"  

# here integer 0L is needed instead of real 0.0 
# manyNumbersWithNA contains integer numbers and the method complains
if_else( manyNumbersWithNA >= 500, manyNumbersWithNA, 0L ) 

 [1]  NA 710 914 874   0   0  NA 529 528 546 526 913 724  NA 631   0   0   0   0   0   0   0 960

Duplicates and unique elements

• Input: a vector

unique( duplicatedNumbers )

[1] 2 3 4 5 1

unique( c( NA, duplicatedNumbers, NA ) )

[1] NA  2  3  4  5  1

duplicated( duplicatedNumbers )

 [1] FALSE FALSE FALSE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE

Positions of max/min elements

which.max( manyNumbersWithNA )

[1] 23

manyNumbersWithNA[ which.max( manyNumbersWithNA ) ]

[1] 960

which.min( manyNumbersWithNA )

[1] 20

manyNumbersWithNA[ which.min( manyNumbersWithNA ) ]

[1] 74

range( manyNumbersWithNA, na.rm = TRUE )

[1]  74 960

Sorting/ordering of vectors

manyNumbersWithNA

 [1]  NA 710 914 874 204 164  NA 529 528 546 526 913 724  NA 631  77 453 174 471  74 455 103 960

sort( manyNumbersWithNA )

 [1]  74  77 103 164 174 204 453 455 471 526 528 529 546 631 710 724 874 913 914 960

sort( manyNumbersWithNA, na.last = TRUE )

 [1]  74  77 103 164 174 204 453 455 471 526 528 529 546 631 710 724 874 913 914 960  NA  NA  NA

sort( manyNumbersWithNA, na.last = TRUE, decreasing = TRUE )

 [1] 960 914 913 874 724 710 631 546 529 528 526 471 455 453 204 174 164 103  77  74  NA  NA  NA

manyNumbersWithNA[1:5]

[1]  NA 710 914 874 204

order( manyNumbersWithNA[1:5] )

[1] 5 2 4 3 1

rank( manyNumbersWithNA[1:5] )

[1] 5 2 4 3 1

sort( mixedLetters )

 [1] "A" "b" "c" "e" "G" "H" "J" "l" "N" "r"

Ranking of vectors

manyDuplicates <- sample( 10:15, 10, replace = TRUE )
rank( manyDuplicates )

 [1]  5.5  3.0  3.0 10.0  3.0  8.0  5.5  8.0  8.0  1.0

rank( manyDuplicates, ties.method = "min" )

 [1]  5  2  2 10  2  7  5  7  7  1

rank( manyDuplicates, ties.method = "random" )

 [1]  5  3  4 10  2  7  6  9  8  1

Rounding numbers

v <- c( -1, -0.5, 0, 0.5, 1, rnorm( 10 ) )
v

 [1] -1.0000000 -0.5000000  0.0000000  0.5000000  1.0000000  0.1873370 -0.3493287  0.3487434  1.3830733
[10]  1.1596234 -1.8043173 -0.4060881 -0.2844329 -0.8486468  0.2763056

round( v, 0 )

 [1] -1  0  0  0  1  0  0  0  1  1 -2  0  0 -1  0

round( v, 1 )

 [1] -1.0 -0.5  0.0  0.5  1.0  0.2 -0.3  0.3  1.4  1.2 -1.8 -0.4 -0.3 -0.8  0.3

round( v, 2 )

 [1] -1.00 -0.50  0.00  0.50  1.00  0.19 -0.35  0.35  1.38  1.16 -1.80 -0.41 -0.28 -0.85  0.28

floor( v )

 [1] -1 -1  0  0  1  0 -1  0  1  1 -2 -1 -1 -1  0

ceiling( v )

 [1] -1  0  0  1  1  1  0  1  2  2 -1  0  0  0  1

Naming vector elements

heights <- c( Amy = 166, Eve = 170, Bob = 177 )
heights

Amy Eve Bob 
166 170 177 

names( heights )

[1] "Amy" "Eve" "Bob"

names( heights ) <- c( "AMY", "EVE", "BOB" )
heights

AMY EVE BOB 
166 170 177 

heights[[ "EVE" ]]

[1] 170

Generating grids

expand_grid( x = c( 1:3, NA ), y = c( "a", "b" ) )

# A tibble: 8 x 2
      x y    
  <int> <chr>
1     1 a    
2     1 b    
3     2 a    
4     2 b    
5     3 a    
6     3 b    
7    NA a    
8    NA b    

Generating combinations

combn( c( "a", "b", "c", "d", "e" ), m = 2, simplify = TRUE )

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "a"  "a"  "a"  "a"  "b"  "b"  "b"  "c"  "c"  "d"  
[2,] "b"  "c"  "d"  "e"  "c"  "d"  "e"  "d"  "e"  "e"  

combn( c( "a", "b", "c", "d", "e" ), m = 3, simplify = TRUE )

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "a"  "a"  "a"  "a"  "a"  "a"  "b"  "b"  "b"  "c"  
[2,] "b"  "b"  "b"  "c"  "c"  "d"  "c"  "c"  "d"  "d"  
[3,] "c"  "d"  "e"  "d"  "e"  "e"  "d"  "e"  "e"  "e"  

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